Sunday, February 8, 2009

Energy From Moving Water

by Alan S. Cajes
Moving water is one of the oldest sources of energy. It was used thousands of years ago to turn a paddle wheel for such purposes as grinding grain. At present, power produced by moving water or hydropower is used to generate electricity. Compared to the other renewable energy sources, moving water is the most often used resource to generate electricity. The wide use of hydropower was made possible by the availability of the technology to transmit electricity over long distances. In the past, a hydroelectric power plant is not feasible because a plant must be located on a water resource, which is often far from the houses and businesses.

Water that flows through rivers and tapped for electricity generation is part of the water cycle. The sun heats water on the surface and causes it to evaporate. When it reaches the atmosphere, the water vapor condenses into clouds and falls back onto the surface as precipitation.

We derive mechanical energy from moving water by directing, harnessing or channeling it. The amount of available energy in moving water is determined by its flow or fall. Swiftly flowing water in a big river or water descending rapidly from a very high point carry a great deal of energy in its flow. Water flows through a pipe or penstock. It then pushes against and turns blades in a turbine to spin a generator to produce electricity. In a run-of-the-river system, the force of the current applies the needed pressure. In a storage system, water is collected in reservoirs created by dams and then released when the demand for electricity is high.

The first hydropower project in the Philippines, the Camp John Hay Hydroelectric Power Plant with an installed capacity of 560 kilowatts, was established by missionaries in Baguio City in 1913. In 2006, the country’s installed generating capacity from hydropower is 3,257 megawatts. It is 20.6 percent of the total installed generating capacity of the country. The total untapped hydropower resource potential of the Philippines ranges from 10,500 to 13,000 megawatts or more.

Although hydropower is almost free, has no waste products and does not pollute the water or the air, hydropower plants do change the environment and affect natural habitats. For instance, in a river system, some species of fish must swim upstream to their spawning grounds to reproduce, but the series of dams gets in their way. Proper environmental planning must be done, therefore, to prevent or mitigate the negative environmental impacts in the construction and operation of hydropower plants.

Sources: Energy Information Administration, Electric Power Monthly, March 2007; National Energy Education Development Project, Intermediate Energy Infobook, 2004-2005.